Endoscope with an improved working channel

ABSTRACT

A medical device includes an insertion tube, having a proximal end and a distal end, which is configured for insertion into a body cavity of a subject. An optical assembly is contained in the distal end and configured to form an image of a target region in the body cavity. A working channel passes through the insertion tube and is configured to convey a fluid from the proximal to the distal end. The working channel has a segment adjacent to the distal end that is narrowed so as to cause the fluid to exit the working channel into the target region in a diverging cone.

CLAIM OF PRIORITY

This application is a continuation of Ser. No. 12/637,513 filed on Dec.14, 2009, and claims priority therefrom incorporated herein byreference.

BACKGROUND

The present inventive subject matter relates generally to medicalinstruments, and specifically to endoscopic devices and methods.

Endoscopes commonly contain a working channel, which may be used tointroduce specially-designed diagnostic and therapeutic instruments intothe area under view inside the body. In some systems, the workingchannel may be connected to a pump outside the body and used for suctionor fluid delivery (irrigation) to the area of the distal tip of theendoscope. For example, a clear fluid, such as saline solution, may beinjected through the working channel in order to clean the endoscopeviewing window and/or clear debris from the area under view.

PCT International Publication WO 03/053226, whose disclosure isincorporated herein by reference, describes an endoscope for use inintravascular photographic imaging. In one embodiment, a fluid isinjected via an open channel in order to dilute the blood in thevicinity of a target region to be imaged. A control unit controls theamount of injected fluid according to whether the imaging data meets apredetermined threshold of resolution or other measure of quality.

U.S. Patent Application Publication 2001/0004692, whose disclosure isincorporated herein by reference, describes an endoscopic sprayinginstrument, which can spray liquid uniformly over all directions. Arotatingly-guiding groove at the leading end of a liquid-supplying tubeis rotated about an central axis within a liquid-rotating chamber at theleading end. The liquid is discharged forwardly from an ejection holeformed in the wall of the liquid-rotating chamber. An annular, protrudedwall is spaced outwardly from the outer periphery of the ejection hole.

SUMMARY

Embodiments of the present inventive subject matter that are describedhereinbelow provide devices and methods for controlling and efficientlyexploiting the flow of fluid through an endoscope working channel.

There is therefore provided, in accordance with an embodiment of thepresent inventive subject matter, a medical device, including aninsertion tube, having a proximal end and a distal end, which isconfigured for insertion into a body cavity of a subject. An opticalassembly is contained in the distal end and is configured to form animage of a target region in the body cavity. A working channel passesthrough the insertion tube and is configured to convey a fluid from theproximal to the distal end, and has a segment adjacent to the distal endthat is narrowed so as to cause the fluid to exit the working channelinto the target region in a diverging cone.

In a disclosed embodiment, the working channel includes a convergingsegment proximal to the narrowed segment and a diverging segment distalto the narrowed segment, such that the converging, narrowed anddiverging segments together define a Venturi tube. Additionally oralternatively, the working channel has an inner surface in which spiralgrooves are formed so as to cause a vortical flow of the fluid throughthe narrowed segment.

In some embodiments, the working channel is configured to accommodate atool, which is passed through the working channel into the target regionwhile the fluid irrigates the target region. The tool may include anobstructing element, which is positioned at the distal end of theworking channel so as to narrow the segment adjacent to the distal end.

Additionally or alternatively, the apparatus includes a fluid sensor,which is configured to measure a characteristic of a flow of the fluidthrough the working channel.

There is also provided, in accordance with an embodiment of the presentinventive subject matter, medical apparatus, including an endoscope,which includes an insertion tube, having a proximal end and a distalend, which is configured for insertion into a body cavity of a subject.The endoscope contains a working channel, which is configured to conveya fluid from the proximal end to a target region in the body cavityadjacent to the distal end. A fluid sensor is configured to measure acharacteristic of a flow of the fluid through the working channel. Acontrol unit is configured to regulate the flow of the fluid through theworking channel responsively to the measured characteristic.

In disclosed embodiments, the endoscope includes an optical assemblycontained in the distal end and configured to form an image of thetarget region, and the control unit is configured to process the imageand to regulate the flow of the fluid through the working channelresponsively to a quality of the image. Typically, the control unit isconfigured to set the flow automatically, responsively to the measuredcharacteristic and the quality of the image, so as to maximize acontrast of the image while minimizing a rate of the flow, withinrespective, predetermined upper and lower limits of the rate andcontrast.

In one embodiment, the fluid sensor is contained in the distal end ofthe endoscope. In an alternative embodiment, the fluid sensor is coupledto the working channel outside the proximal end of the endoscope. Thefluid sensor may include a pressure sensor, or it may be configured tomeasure a rate of flow of the fluid through the working channel.

There is additionally provided, in accordance with an embodiment of thepresent inventive subject matter, a method for medical treatment,including providing an endoscope having a distal end for insertion intoa body cavity of a subject, the distal end containing an opticalassembly configured to form an image of a target region in the bodycavity. A fluid is conveyed through a working channel, which passes froma proximal end of the endoscope to the distal end and has a segmentadjacent to the distal end that is narrowed so as to cause the fluid toexit the working channel into the target region in a diverging cone.

There is further provided, in accordance with an embodiment of thepresent inventive subject matter, a method for medical treatment,including providing an endoscope having a distal end for insertion intoa body cavity of a subject and containing a working channel forconveying a fluid from a proximal end of the endoscope to a targetregion in the body cavity adjacent to the distal end. A characteristicof a flow of the fluid through the working channel is measured, and theflow of the fluid through the working channel is regulated responsivelyto the measured characteristic.

The present inventive subject matter will be more fully understood fromthe following detailed description of the embodiments thereof, takentogether with the drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a system for endoscopy, in accordancewith an embodiment of the present inventive subject matter;

FIG. 2 is a schematic cutaway view of a nozzle used in an endoscope, inaccordance with an embodiment of the present inventive subject matter;

FIG. 3 is a schematic sectional view of the distal end of an endoscope,in accordance with another embodiment of the present inventive subjectmatter;

FIG. 4 is a block diagram that schematically illustrates components usedfor flow control in a system for endoscopy, in accordance with anembodiment of the present inventive subject matter; and

FIG. 5 is a flow chart that schematically illustrates a method for flowcontrol, in accordance with an embodiment of the present inventivesubject matter.

DETAILED DESCRIPTION

In many endoscopic procedures, the target region that is viewed by theendoscope is irrigated to remove blood and debris so as to give theoperator (typically a physician) a clear picture of the region. Thisirrigation is carried out through a working channel of the endoscope,which may also be used (even simultaneously) for insertion of endoscopictools into the target region. It is desirable that the fluid exit theworking channel in a wide, uniform cone in order to effectively irrigatethe entire target region.

Some embodiments of the present inventive subject matter, as describedhereinbelow, address the need for effective irrigation, and providesolutions that are effective even when an endoscopic tool is alsopresent in the working channel. In these embodiments, the workingchannel has a segment adjacent to the distal end of the endoscope thatis narrowed so as to cause the fluid to spread from the working channelinto the target region in a diverging cone. In some embodiments, theworking channel comprises a converging segment proximal to the narrowedsegment and a diverging segment distal to the narrowed segment, thusdefining a Venturi tube. In other embodiments, the tool comprises anobstructing element, such as a collar, which is positioned at the distalend of the working channel so as to narrow the adjacent segment of theworking channel. The inner surface of the working channel may also beconfigured to cause a vortical flow of the fluid (i.e., swirling aroundthe axis of the channel) through the narrowed segment of the workingchannel, which further enhances the spread of the exiting fluid.

Excessive irrigation is undesirable, as it can overload the patient'sbody with fluid. Therefore, in some embodiments of the present inventivesubject matter, a control unit regulates the flow of the irrigationfluid so as to use the minimal amount of fluid necessary to give imagesof sufficient quality. For this purpose a fluid sensor measures acharacteristic of the fluid flow through the working channel, such asthe pressure or flow rate. The control unit monitors this flowcharacteristic, as well as the quality of the image (as expressed, forexample, by a measure of image contrast), and adaptively increases anddecreases the fluid flow as required, within predetermined bounds, toreach the desired balance between fluid flow and image quality. Thecontrol unit may carry out these functions automatically, without activeinvolvement of the operator.

FIG. 1 is a schematic side view of a system 20 for endoscopy, inaccordance with an embodiment of the present inventive subject matter.The system comprises an endoscope 22, which is connected at its proximalend to a control console 24. The endoscope comprises a flexibleinsertion tube 23, having a distal end 26 (shown in a detailed sectionalview in the inset in FIG. 1) for insertion into a body cavity. In thepresent embodiment, it will be assumed that endoscope 22 is aureteroscope, which is designed for insertion through the patient'surethra, bladder and ureter to the renal pelvis. This sort of endoscopeis generally restricted to a small diameter, typically no greater than 3mm, which accordingly limits the number and size of working channels andother functional components that can be accommodated in the endoscope.Alternatively, the principles of the present inventive subject mattermay be applied in endoscopes of other types.

Distal end 26 contains an optical assembly 27 of a type that isdescribed, for example, in PCT International Publication WO 03/098913,whose disclosure is incorporated herein by reference. Briefly, anoptical objective 28 collects light from a target region outside thedistal end and focuses the light via a turning mirror 30 (shown here inthe form of a prism) onto an image sensor 32, whose focal plane isparallel to the longitudinal axis of insertion tube 23. The image sensoris mounted on a circuit board 34, which is connected by wires 36 runningthrough the endoscope to console 24. Distal end 26 typically alsocontains one or more light sources (not shown) for illuminating thetarget region.

This optical assembly is shown in FIG. 1 by way of example, and theprinciples of the present inventive subject matter may similarly beapplied in conjunction with other types of endoscopic optical assembliesthat are known in the art. For example, the focal plane of the imagesensor may be perpendicular to the axis of the insertion tube, as inmost endoscopes that are known in the art. As another example, theoptical assembly in the distal end of the endoscope may comprise animage guide, such as a fiberoptic bundle, which conveys the imagecaptured by the optical objective to a camera head at the proximal endof the endoscope. The endoscope itself may be rigid, rather thanflexible as shown here.

A working channel 38 passes through insertion tube 23 from the proximalend (at console 24) to distal end 26. This working channel may be usedboth to pass endoscopic tools through endoscope 22, to operate in thetarget region, and to irrigate the target region. For the latterpurpose, the working channel ends in a nozzle 40 at the distal end. Thenozzle contains a narrowed segment adjacent to the distal end, whichcauses the irrigation fluid to exit the working channel into the targetregion in a diverging cone, as described in greater detail hereinbelow.A pump 48 in console 24 drives fluid through the working channel at acontrollable rate.

Console 24 comprises a camera control unit (CCU) 44, which receives andprocesses the signals carried from optical assembly 27 over wires 36 inorder to generate output images of the target region. The images may bedisplayed on a screen 46. The CCU may also extract indicators of imagequality, such as a measure of the image contrast, and may use theseindicators in controlling the flow of the irrigation fluid driven bypump 48, as described in detail hereinbelow. CCU 44 typically comprisesa general-purpose or embedded microprocessor, with input and outputcircuits for communicating with the other elements of system 20. CCUdevices that are known in the art may be used for this purpose, with thepossible addition of input/output connections for pressure measurementand flow control, as well as suitable software to carry out thefunctions that are described hereinbelow. Alternatively, these functionsmay be performed by dedicated or programmable hardware logic.

Endoscope 22 contains a fluid sensor 42, which measures a characteristicof the fluid flowing through working channel 38. For example, sensor 42may be a miniature pressure sensor, which measures the fluid pressureinside the working channel (as shown in FIG. 1) or in the target regionoutside the distal end of the endoscope. One type of pressure sensorthat may be used for this purpose is a Samba MicroC 420 UD transducer(produced by Samba Sensors AB, Goteborg, Sweden), comprising an opticalfiber with a pressure-sensitive optical cavity at its distal tip. Thesensor may be deployed in the working cavity as shown in FIG. 1, or itmay alternatively be integrated within the body of insertion tube 23. Aslong as the flow characteristics of working channel 38 are known, thepressure measurement gives a reliable indicator of the flow rate.

Alternatively, sensor 42 may measure flow rate by other means. Forexample, sensor 42 may comprise a heating element and a temperaturesensor, which indicates the rate of flow based on the rate at which thefluid flowing through the working channel cools the heating element.Alternatively or additionally, a pressure sensor 50 or other flowsensing element may be coupled to the working channel outside theproximal end of endoscope 22. For example, sensor 50 may be integratedwith console 24, as shown below in FIG. 4.

FIG. 2 is a schematic cutaway view showing details of nozzle 40, inaccordance with an embodiment of the present inventive subject matter.The nozzle has the form of a Venturi tube, with a narrow waist 62preceded by a converging segment (to the left in the figures) andfollowed by a diverging segment (to the right), so that the irrigationfluid is emitted from the nozzle to form an expanding cone 64. A varietyof types of Venturi tubes, as well as methods for designing such tubes,are known in the art. Representative examples are presented in U.S. Pat.Nos. 4,092,003; 5,618,001; 5,106,022; 6,042,026; 6,860,438; and7,051,524, as well as in U.S. Patent Application Publications2001/0004692; 2007/0278331; and 2007/0290073, all of whose disclosuresare incorporated herein by reference.

In the present case, the inventors have found that an effective conicalspread of the emitted fluid can be achieved using the followingparameters, wherein dimensions are relative to the diameter of waist 62,which is identified as “X”:

-   -   Length of waist X−5.5X.    -   Convergence angle of converging segment −21±2°.    -   Diameter of converging segment −2X−2.5X.    -   Divergence angle of diverging segment −5−15°.    -   Diameter of diverging segment X−3X.        The optimal dimensions may be found in each case based on the        specific geometrical constraints of the endoscope, using        techniques described in the above-mentioned references.

Furthermore, to broaden the spread of the fluid exiting nozzle 40 incone 64, the nozzle may contain spiral grooves 60 within its innersurface. These grooves introduce a vortical component (swirling motion)in the fluid flow, which enhances the fluid spread without significantlyobstructing channel 38.

FIG. 3 is a schematic sectional view of distal end 26 of an endoscope,in accordance with an embodiment of the present inventive subjectmatter. In this embodiment, a tool 70, such as an optical fiber fordelivering laser radiation, is inserted through working channel 38. Thetool has an obstructing element, in the form of a collar 72, whichsignificantly narrows the distal segment of the working channel at itsoutlet. The collar may be integrally formed as part of tool 70, or itmay be fitted onto the tool as required. The obstructing element has theeffect of spreading the flow of the irrigation fluid into a cone, whoseangular spread may be controlled by advancing and retracting tool 70.The particular size and shape of collar 72 are shown in FIG. 3 solely byway of example, and other sizes and shapes may be used, as well.

FIG. 4 is a block diagram that schematically illustrates components thatmay be used for flow control in system 20, in accordance with analternative embodiment of the present inventive subject matter. In thisexample, pump 48 and pressure sensor 50 are connected to a fluid supplytube 76, which connects to working channel 38 at the proximal end ofendoscope 22. An electronically-controlled valve 78 is normally openwhile pump 48 is in operation, so that sensor 50 measures the pumpoutlet pressure. Periodically, however, CCU 44 commands valve 78 toclose momentarily and takes a pressure reading from sensor 50, which inthis case is indicative of the outlet pressure from working channel 38.This pressure reading may be used in addition to or instead of a readingby a sensor in the endoscope itself.

Additionally or alternatively, a volumetric flow rate sensor may beconnected to tube 76.

FIG. 5 is a flow chart that schematically illustrates a method for flowcontrol, in accordance with an embodiment of the present inventivesubject matter. The method is described herein, for the sake of clarity,with reference to the elements of system 20 that are shown and describedabove. Alternatively, however, the method may be implemented insubstantially any endoscopic system with appropriate components formaking flow and image quality measurements.

At each cycle of the method, CCU 44 makes a measurement of imagequality, at a quality measurement step 80. In the present embodiment,the measure is based on the local contrast level in the image. A measureof contrast may be derived, for example, as follows:

-   -   Divide the image into 8×8 blocks.    -   For each block calculate the difference between the maximum        pixel intensity and the minimum pixel intensity.    -   Average the result over all the 8×8 blocks. This is the local        contrast value.        Alternatively or additionally, the CCU may derive other measures        of contrast, as well as other types of image quality measures        that are known in the art.

CCU 44 compares the contrast measurement to a preset upper threshold H,at an high contrast checking step 82. If the contrast is above thethreshold, meaning that the picture is relatively sharp, the CCU checksthe irrigation flow rate, at a low flow checking step 84. If the flow isabove a preset minimum value, the CCU instructs pump 48 to decrease theflow rate by a predetermined increment, at a flow reduction step 86. Thepurpose of this step is to reduce the flow to the lowest rate that willmaintain high image quality, thereby reducing unnecessary fluid loadingof the patient's body. If the pump is already set to the minimum flowrate, the rate remains unchanged. In either case, the method returns tostep 80.

On the other hand, if CCU 44 determines at step 82 that the measuredcontrast is below the upper threshold, it proceeds to check whether thecontrast is below a preset lower threshold L, at a low contrast checkingstep 88. If the contrast is below the threshold, meaning that thepicture is relatively blurry, the CCU checks the irrigation flow rate,at a high flow checking step 90. If the flow is below a preset maximumvalue, the CCU instructs pump 48 to increase the flow rate by apredetermined increment, at a flow increase step 92, so as to moreeffectively clear the target region of blood and debris. If the pump isalready set to the maximum flow rate, the rate remains unchanged. Themethod then returns to step 80, and the cycle repeats.

It will be appreciated that the embodiments described above are cited byway of example, and that the present inventive subject matter is notlimited to what has been particularly shown and described hereinabove.Rather, the scope of the present inventive subject matter includes bothcombinations and subcombinations of the various features describedhereinabove, as well as variations and modifications thereof which wouldoccur to persons skilled in the art upon reading the foregoingdescription and which are not disclosed in the prior art.

What is claimed is:
 1. Medical apparatus, comprising: an endoscope,comprising an insertion tube, having a proximal end and a distal end,which is configured for insertion into a body cavity of a subject, andcontaining a working channel, which conveys a liquid from the proximalend to a target region in the body cavity adjacent to the distal end; afluid sensor, contained in the distal end of the endoscope, whichmeasures a rate of flow of the liquid in the working channel; and acontrol unit which is configured to regulate the flow of the liquid inthe working channel responsively to the measured rate of flow; whereinthe working channel has a segment adjacent to the distal end of theendoscope that is narrowed, a converging segment proximal to thenarrowed segment, and a diverging segment distal to the narrowedsegment, thus defining a Venturi tube; wherein the diameter of theconverging segment narrows from about 2.5 times greater than thediameter of the narrowed segment to about the same diameter as thenarrowed segment; wherein the diameter of the diverging segment expandsfrom about the same diameter as the narrowed segment to about 3 timesgreater than the diameter of the narrowed segment; and the liquid exitsthe working channel in a divergent cone to irrigate the entire targetregion such that it clears blood and/or debris.
 2. The apparatusaccording to claim 1, wherein the endoscope comprises an opticalassembly contained in the distal end and configured to form an image ofthe target region, and wherein the control unit is configured to processthe image and to regulate the flow of the fluid through the workingchannel responsively to a quality of the image.
 3. The apparatusaccording to claim 2, wherein the control unit is configured to set theflow automatically, responsively to the rate of flow and the quality ofthe image, so as to maximize a contrast of the image while minimizing arate of the flow, within respective, predetermined upper and lowerlimits of the rate and contrast.
 4. A method for medical treatment,comprising: providing an endoscope having a distal end for insertioninto a body cavity of a subject and containing a working channel forconveying a liquid from a proximal end of the endoscope to a targetregion in the body cavity adjacent to the distal end; measuring a rateof flow of the liquid in the working channel, wherein measuring the rateof the flow comprises receiving a reading from a fluid sensor containedin the distal end of the endoscope; and regulating the flow of theliquid in the working channel responsively to the measured rate of flow;wherein the working channel has a segment adjacent to the distal end ofthe endoscope that is narrowed, a converging segment proximal to thenarrowed segment and a diverging segment distal to the narrowed segmentthus defining a Venturi tube; wherein the diameter of the convergingsegment narrows from about 2.5 times greater than the diameter of thenarrowed segment to about the same diameter as the narrowed segment;wherein the diameter of the diverging segment expands from about thesame diameter as the narrowed segment to about 3 times greater than thediameter of the narrowed segment; and the liquid exits the workingchannel in a divergent cone to irrigate the entire target region suchthat it clears blood and/or debris.
 5. The method according to claim 4,wherein the endoscope comprises an optical assembly contained in thedistal end and configured to form an image of the target region, andwherein regulating the flow comprises measuring a quality of the imageand regulating the flow of the liquid through the working channelresponsively to the measured quality of the image.
 6. The methodaccording to claim 5, wherein regulating the flow comprises setting theflow automatically, responsively to the rate of flow and the measuredquality, so as to maximize a contrast of the image while minimizing arate of the flow, within respective, predetermined upper and lowerlimits of the rate and contrast.
 7. Medical apparatus, comprising: anendoscope, comprising an insertion tube, having a proximal end and adistal end, which is configured for insertion into a body cavity of asubject, and containing a working channel, which conveys a liquid fromthe proximal end to a target region in the body cavity adjacent to thedistal end; a fluid sensor, which measures a rate of flow of the liquidin the working channel; and a control unit, which is configured toregulate the flow of the liquid in the working channel responsively tothe measured rate of flow; wherein the fluid sensor is contained in thedistal end of the endoscope; the working channel ends in a nozzle at thedistal end; the nozzle includes a narrowed segment adjacent to thedistal end; the liquid exits the working channel in a divergent cone toirrigate the entire region such that it clears blood and/or debris; andthe insertion tube has a diameter about equal to or about less than 3mm.
 8. The apparatus according to claim 7, wherein the endoscopecomprises an optical assembly contained in the distal end and configuredto form an image of the target region, and wherein the control unit isconfigured to process the image and to regulate the flow of the liquidthrough the working channel responsively to a quality of the image. 9.The apparatus according to claim 8, wherein the control unit isconfigured to set the flow automatically, responsively to the rate offlow and the quality of the image, so as to maximize a contrast of theimage while minimizing the rate of the flow, within respective,predetermined upper and lower limits of the rate and contrast.